I'm trying to call multiple parameters (self, other) in a __str__() function defined in a class but I keep getting an error - python-2.x

Question

As stated above, I'm currently trying to print multiple values inside of a string function using the (self, other) process, but I keep getting this error:
TypeError: str() takes exactly 2 arguments (1 given)
Here is my relevant code block:
def __str__(self, enemy):
s = "{} vs {}\n\n".format(self.name, enemy.name)
s += "Your move set: "
for move in self.moves.keys():
s += move + " - "
s += "\n\n"
s += "Current health: {}\n\n".format(self.health)
s += "Enemy health: {}\n\n".format(enemy.health)
return s
This is how I'm calling the function, obviously with the fat trimmed out.
c1 = Fighter("Gunsmith" , "gunsmith.gif")
Main.character = c1
statsList.insert(END, str(self.character))
The code works if I delete enemy from the parameters and all other enemy.x parameters.
https://pastebin.com/7dWi2DpB
my full code, as its too detailed to link multiple parts.
heres the full error:
Exception in Tkinter callback
Traceback (most recent call last):
File "C:\Python27\lib\lib-tk\Tkinter.py", line 1547, in __call__
return self.func(*args)
File "C:\Users\CornTortilla\Desktop\Comp. Science\CSC132\Github\teamProject\Pi.py", line 197, in chooseGunsmith
self.fightWindow()
File "C:\Users\CornTortilla\Desktop\Comp. Science\CSC132\Github\teamProject\Pi.py", line 180, in fightWindow
statsList.insert(END, str(self.character))
TypeError: __str__() takes exactly 2 arguments (1 given)